Inks have been used to mark items for a number of purposes, for example, for determining their authenticity. Such markings, e.g., covert markings, are used, for example, to identify goods that are intended for sale in a particular market. These markings are intended to prevent profit through the selling of goods for higher margins in a higher value market that were originally distributed for sale in a lower value market. Covert marking applications typically require that the markings are both invisible to the human eye and completely irreproducible in the event that the marking is discovered. It is often desirable after such security features are read that the security feature can be deactivated. The ready and predictable deactivation of a mark lends to the security of the system incorporating that mark for a number of reasons. First, it is an added feature of the mark that lends to the irreproducibility (or unauthorized reproduction) of the mark. Second, by the deactivation, the marks are not transferable to other items or locations after their intended use within the security network. Third, the information contained in the mark is destroyed and cannot be read or reproduced by unauthorized parties.
The deactivation of the security feature may denote one of several events. An example of such an event would be to inform the holder of an article that the article is no longer intended for sale in a given market. Still another reason to deactivate a mark would be to render an article valueless after it has been redeemed for cash value.
Markings are also desirable for process control in production or distribution environments. For example, articles may be sorted by reading their identifying markings at very high throughput speeds in centralized distribution facilities. In production processes, it may be desirable to distinguish articles that have undergone one process from articles that have undergone another process. Another example of process control would be for process monitoring. For example, one commonly used process control ink serves as an indicator on sealed containers of products that distinguishes containers that have undergone a sterilization process from those which have not undergone such sterilization process. These processes could be, for example, either steam induced or ultraviolet light induced. The ink marks typically change color and provide a visual indication that an article has passed the process. Such visual monitoring could require the employment of a line operator to monitor the products online. There is a need for machine-readable inks and marks that indicate the progress of such processes.
In addition to the alteration of a machine-readable component, a visibly changing component might be desirable for certain applications where no machine readability is possible. Currently available marking systems that provide both a visual and a fluorescent indicator require two separate inks each with their own applicator. It would be desirable for the design of an ink that could be used for these multiple purposes—e.g., color change and luminescence change—to have both the colored component and the fluorescent colorant (e.g., dye) together in a single system. It would be further desirable that the changes in the two dyes occur simultaneously. This would allow for the application of the mark on production lines using a single applicator, such as an ink jet ink printer. The use of a single fluid with a single applicator is highly desirable in the design of a security system so that any breech in the integrity of the system—i.e., fluids that are stolen for use elsewhere—can be quickly identified.
One manner in which the value or process status of an item could be changed via a luminescent or colored mark would be to render the mark unreadable. One method to accomplish this would be to discolor, bum, or otherwise destroy the mark by applying energy to it. Conventional dyes or pigments would not necessarily react with the applied energy directly. The degree to which these would react with applied energy would depend on their inherent stability. The decomposition of many organic substances can be brought about thermally with temperatures beneath about 600° C. Many substrates, namely plastics and paper, begin to decompose at temperatures in excess of about 150° C. The heat sources typically used are radiative sources composed of filaments that must be heated through input of electrical energy. These sources are slow to respond to demands for energy and are usually operated in practice in a semi-powered ready mode from which they can be made operational more quickly. These units are impractical for some automated processes, such as sorting on a production line, due to the continuous need for power in ready mode and low efficiency via radiative heat loss. There exists a need for a system which requires less energy to operate
By way of background, attempts have been made in general to provide security markings, see, for example, U.S. Pat. Nos. 6,441,380; 6,402,986; and 5,837,042. There is a need for a method of providing an authentication mark which can be rendered unreadable and an ink jet ink composition that is suitable for printing on substrates such authentication marks.
The invention provides ink compositions suitable for fulfilling one or more of the above needs. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.